Refrigeration/air conditioning equipment

ABSTRACT

Refrigeration/air conditioning equipment includes a first internal heat exchanger for exchanging heat between a refrigerant to be sucked in a compressor and a high-pressure liquid refrigerant, an injection circuit for evaporating a bypassed high-pressure liquid at intermediate pressure and injecting the vaporized refrigerant into the compressor, a second internal heat exchanger for exchanging heat between the high-pressure liquid refrigerant and the refrigerant to be injected, and a heat source for heating the refrigerant to be injected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to refrigeration/air conditioningequipment, and particularly to refrigeration/air conditioning equipmentin which the heating capacity at low outdoor temperature is improved bygas injection, and a defrosting operation is performed efficiently.

2. Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2001-304714discloses refrigeration/air conditioning equipment including agas-liquid separator in an intermediate-pressure portion between acondenser and an evaporator. A gas refrigerant separated by thegas-liquid separator is injected into an intermediate-pressure portionof a compressor to increase the heating capacity.

Japanese Unexamined Patent Application Publication No. 2000-274859discloses another conventional refrigeration/air conditioning equipmentwithout a gas-liquid separator. In this equipment, part of ahigh-pressure liquid refrigerant is bypassed, is decompressed, isvaporized through heat exchange with the high-pressure liquidrefrigerant. The vaporized refrigerant is injected into a compressor toincrease the heating capacity.

Japanese Unexamined Patent Application Publication No. 2001-263882discloses still another conventional refrigeration/air conditioningequipment, in which a heater for heating a refrigerant is provided toimprove the efficiency in a defrosting operation.

However, these pieces of conventional refrigeration/air conditioningequipment have the following problems.

First, as described in the Japanese Unexamined Patent ApplicationPublication No. 2001-304714, when the injection is performed with thegas-liquid separator, the fluid volume in the gas-liquid separatorvaries with the amount of the injection. This variation causesfluctuations in the distribution of a liquid refrigerant level in arefrigeration cycle and makes the operation unstable.

When the flow rate of a gas refrigerant to be injected is substantiallyequal to the flow rate of a gas refrigerant in a two-phase refrigerantflowing into the gas-liquid separator, only the liquid refrigerant flowsout to an evaporator and therefore the liquid refrigerant level in thegas-liquid separator is substantially constant. However, when the flowrate of the gas refrigerant to be injected is smaller than that of thegas refrigerant flowing into the gas-liquid separator, the gasrefrigerant also flows out to the evaporator from the bottom of thegas-liquid separator. Thus, most of the liquid refrigerant in thegas-liquid separator flows out. Conversely, when the flow rate of therefrigerant to be injected increases and the gas refrigerant becomesdeficient, the liquid refrigerant is also injected into the compressor.Thus, the liquid refrigerant flows out from the top of the gas-liquidseparator, and the gas-liquid separator is almost filled with the liquidrefrigerant.

The injection flow rate tends to vary, for example, with the pressure ofthe refrigeration cycle, the pressure of the gas-liquid separator, orthe operation capacity of the compressor. Thus, the injection flow ratehardly balances with the flow rate of the gas refrigerant flowing intothe gas-liquid separator. Actually, the liquid refrigerant level in thegas-liquid separator tends to vary with the operation and be almost zeroor full. This variation often causes fluctuations in the distribution ofthe refrigerant in the refrigeration cycle, making the operationunstable. Furthermore, the heater as in the Japanese Unexamined PatentApplication Publication No. 2001-263882 is only used in a defrostingoperation and does not contribute significantly to the increase in thecapacity during a heating operation.

SUMMARY OF THE INVENTION

In view of these problems, it is an object of the present invention toprovide refrigeration/air conditioning equipment that has a higherheating capacity than conventional gas injection cycles, and exhibits asufficient heating capacity even in a cold district where the outdoortemperature is −10° C. or lower, and also to increase the efficiencyduring the defrosting operation.

Refrigeration/air conditioning equipment according to the presentinvention includes:

a compressor;

a four-way valve;

an indoor heat exchanger;

a first decompressor; and

an outdoor heat exchanger,

wherein these components are coupled circularly, and heat is suppliedfrom the indoor heat exchanger,

and the refrigeration/air conditioning equipment further includes:

an intermediate-pressure receiver disposed between the indoor heatexchanger and the first decompressor;

a first internal heat exchanger that exchanges heat between arefrigerant in the intermediate-pressure receiver and a refrigerant in asuction pipe of the compressor; and

an injection circuit in which part of a refrigerant between the indoorheat exchanger and the first decompressor is bypassed and is injectedinto a compression chamber in the compressor,

wherein the injection circuit includes:

-   -   a second decompressor;    -   a second internal heat exchanger that exchanges heat between a        refrigerant having a pressure reduced by the second decompressor        and the refrigerant between the indoor heat exchanger and the        first decompressor; and    -   a heat source for heating a refrigerant disposed between the        second internal heat exchanger and the compressor.

Thus, even when a high flow rate of the gas refrigerant is injected,sufficient heating capacity can be provided even under such a conditionas the heating capacity tends to decrease owing to low outdoortemperature or the like, by preventing the reduction in the dischargetemperature of the compressor and allowing the indoor heat exchanger toexhibit sufficient heat-exchange performance. According to the presentinvention, the gas refrigerant to be injected is supplied not from thegas-liquid separator but through the gasification of the bypassedrefrigerant with the second internal heat exchanger. Thus, the variationin the fluid volume caused by the gas-liquid separator can be avoided.Thus, more stable operation can be achieved. In addition, the gasinjection can be increased while the reduction in the dischargetemperature of the compressor is prevented. Thus, the heating capacityis further increased, and the efficiency during the defrosting operationis improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram of refrigeration/airconditioning equipment according to Embodiment 1 of the presentinvention;

FIG. 2 is a PH diagram showing the heating operation of therefrigeration/air conditioning equipment according to Embodiment 1 ofthe present invention;

FIG. 3 is a PH diagram showing the cooling operation of therefrigeration/air conditioning equipment according to Embodiment 1 ofthe present invention;

FIG. 4 is a flow chart showing the control action during the heatingoperation of the refrigeration/air conditioning equipment according toEmbodiment 1 of the present invention;

FIG. 5 is a flow chart showing the control action during the coolingoperation of the refrigeration/air conditioning equipment according toEmbodiment 1 of the present invention;

FIG. 6 is a PH diagram showing the operation of the refrigeration/airconditioning equipment according to Embodiment 1 of the presentinvention in the presence of gas injection;

FIG. 7 is a diagram showing the temperature change of a condenser in therefrigeration/air conditioning equipment according to Embodiment 1 ofthe present invention in the presence of gas injection;

FIG. 8 is a diagram showing the operation characteristics of therefrigeration/air conditioning equipment according to Embodiment 1 ofthe present invention as a function of the gas-injection flow rate;

FIG. 9 is a diagram showing the operation characteristics of therefrigeration/air conditioning equipment according to Embodiment 1 ofthe present invention with or without a first internal heat exchanger;

FIG. 10 is another diagram showing the operation characteristics of therefrigeration/air conditioning equipment according to Embodiment 1 ofthe present invention as a function of the gas-injection flow rate;

FIG. 11 is a flow chart showing the control action during the heatingand defrosting operation of the refrigeration/air conditioning equipmentaccording to Embodiment 1 of the present invention; and

FIG. 12 is a diagram showing the defrosting operation characteristics ofthe refrigeration/air conditioning equipment according to Embodiment 1of the present invention with or without a first internal heat exchangerand means for heating a refrigerant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a refrigerant circuit diagram of refrigeration/airconditioning equipment of Embodiment 1 according to the presentinvention. In FIG. 1, an outdoor unit 1 includes a compressor 3, afour-way valve 4 for switching between heating and cooling, an outdoorheat exchanger 12, a first expansion valve 11 serving as a firstdecompressor, a second internal heat exchanger 10, a third expansionvalve 8 serving as a third decompressor, an injection circuit 13, asecond expansion valve 14 serving as a second decompressor, anintermediate-pressure receiver 9, and a heat source 17 for heating arefrigerant. A suction pipe 18 of the compressor 3 passes through theintermediate-pressure receiver 9. Thus, a refrigerant in thisthrough-pipe 18a of the suction pipe 18 can exchange heat with arefrigerant 9a in the intermediate-pressure receiver 9. The heat source17 heats a refrigerant circulating through the injection circuit 13.

The capacity of the compressor 3 can be controlled by adjusting thenumber of revolutions with an inverter. The compressor 3 is designedsuch that the refrigerant supplied from the injection circuit 13 can beinjected into a compression chamber in the compressor 3. The firstexpansion valve 11, the second expansion valve 14, and the thirdexpansion valve 8 are electronic expansion valves whose degree ofopening is variable. The outdoor heat exchanger 12 exchanges heat withthe outside air sent by a fan or the like. An indoor unit 2 includes anindoor heat exchanger 6. A gas pipe 5 and a liquid pipe 7 are connectingpipes to connect the outdoor unit 1 and the indoor unit 2. Therefrigeration/air conditioning equipment uses a mixed HFC-basedrefrigerant, R410A as a refrigerant.

The outdoor unit 1 includes a controller 15 and temperature sensors 16.A first temperature sensor 16a is disposed at the discharge side of thecompressor 3, a second temperature sensor 16b is disposed between theoutdoor heat exchanger 12 and the four-way valve 4, a third temperaturesensor 16c is disposed on a refrigerant pass in a intermediate portionof the outdoor heat exchanger 12, a fourth temperature sensor 16d isdisposed between the outdoor heat exchanger 12 and the first expansionvalve 11, a fifth temperature sensor 16e is disposed between theintermediate-pressure receiver 9 and the third expansion valve 8, and asixth temperature sensor 16f is disposed at the suction side of thecompressor 3. These temperature sensors measure the refrigeranttemperatures at their respective installation locations. A seventhtemperature sensor 16g measures the outdoor temperature around theoutdoor unit 1.

An eighth temperature sensor 16h, a ninth temperature sensor 16i, and atenth temperature sensor 16j are disposed in the indoor unit 2. Theeighth temperature sensor 16h is disposed on a refrigerant pass in anintermediate portion of the indoor heat exchanger 6, and the ninthtemperature sensor 16i is disposed between the indoor heat exchanger 6and the liquid pipe 7. These temperature sensors measure the refrigeranttemperatures at their respective installation locations. The tenthtemperature sensor 16j measures the temperature of air sucked into theindoor heat exchanger 6. When the load medium is another medium, such aswater, the tenth temperature sensor 16j measures the temperature of themedium flowing into the indoor heat exchanger 6.

The third temperature sensor 16c and the eighth temperature sensor 16hmeasures the temperatures of the refrigerant in a gas-liquid two phasein the intermediate portion of each heat exchanger, and thereby candetermine the saturation temperatures of the refrigerant under highpressure and low pressure.

The metering and control system 15 in the outdoor unit 1 controls theoperational mode of the compressor 3, pass switching of the four-wayvalve 4, the amount of air sent by a fan in the outdoor heat exchanger12, and the degrees of opening of the first expansion valve, the secondexpansion valve, and the third expansion valve according to the measuredinformation of the temperature sensors 16a to 16j and operatingconditions instructed by a user of the refrigeration/air conditioningequipment.

The operation of the refrigeration/air conditioning equipment will bedescribed below. First, the heating operation will be described withreference to the refrigerant circuit diagram shown in FIG. 1 and the PHdiagram of the heating operation shown in FIG. 2. In the heatingoperation, the flow pass of the four-way valve 4 is set in the directionof the dotted line shown in FIG. 1. A high-temperature high-pressure gasrefrigerant (FIG. 2, point 1) discharged from the compressor 3 flows outfrom the outdoor unit 1 via the four-way valve 4, and flows into theindoor unit 2 through the gas pipe 5. The gas refrigerant flows into theindoor heat exchanger 6, which serves as a condenser, loses its heat,and is condensed to a high-pressure low-temperature liquid refrigerant(FIG. 2, point 2). The heat radiating from the refrigerant istransferred to the load medium, such as air or water, which heats theroom. The high-pressure low-temperature refrigerant flowing out from theindoor heat exchanger 6 flows into the outdoor unit 1 through the liquidpipe 7 and is slightly decompressed with the third expansion valve 8(FIG. 2, point 3), changing into a gas-liquid two-phase refrigerant,which flows into the intermediate-pressure receiver 9. The two-phaserefrigerant transfers heat to a low-temperature refrigerant that is tobe sucked into the compressor 3 in the intermediate-pressure receiver 9,is cooled into a liquid phase (FIG. 2, point 4), and flows out from theintermediate-pressure receiver 9. One part of the liquid refrigerant isbypassed through the injection circuit 13, is decompressed, and isdecreased in temperature through the second expansion valve 14. Theother part of the liquid refrigerant is further cooled by the heatexchange with the bypassed refrigerant in the second internal heatexchanger 10 (FIG. 2, point 5). The other part of the liquid refrigerantis decompressed in the first expansion valve 11 and changes into atwo-phase refrigerant (FIG. 2, point 6). Then, the two-phase refrigerantflows into the outdoor heat exchanger 12, which serves as an evaporator,and absorbs heat to vaporize (FIG. 2, point 7). The gas refrigerantflows through the four-way valve 4, is heated by heat exchange with thehigh-pressure refrigerant in the intermediate-pressure receiver 9 (FIG.2, point 8), and is sucked into the compressor 3.

On the other hand, the refrigerant bypassed through the injectioncircuit 13 is decompressed to an intermediate pressure with the secondexpansion valve 14 and changes into a low-temperature two-phaserefrigerant (FIG. 2, point 9). Then, the low-temperature two-phaserefrigerant exchanges heat with the high-pressure refrigerant in thesecond internal heat exchanger 10, is heated by the heat source 17 (FIG.2, point 10), and is injected into the compressor 3. In the compressor3, the sucked refrigerant (FIG. 2, point 8) is compressed to anintermediate pressure, is heated (FIG. 2, point 11), and is merged intothe injected refrigerant. The merged refrigerant having a reducedtemperature (FIG. 2, point 12) is compressed to a high pressure and isdischarged (FIG. 2, point 1). The heat source 17 for heating arefrigerant can adjust the amount of heat when necessary.

Next, the cooling operation will be described with reference to therefrigerant circuit diagram shown in FIG. 1 and the PH diagram of thecooling operation shown in FIG. 3. In the cooling operation, the flowpass of the four-way valve 4 is set in the direction of the solid lineshown in FIG. 1. A high-temperature high-pressure gas refrigerant (FIG.3, point 1) discharged from the compressor 3 flows into the outdoor heatexchanger 12, which serves as a condenser, via the four-way valve 4. Thegas refrigerant loses its heat and is condensed to a high-pressurelow-temperature refrigerant (FIG. 3, point 2). The high-pressurelow-temperature refrigerant flowing out from the outdoor heat exchanger12 is slightly decompressed with the first expansion valve 11 (FIG. 3,point 3). The refrigerant is cooled by heat exchange with alow-temperature refrigerant flowing through the injection circuit 13 inthe second internal heat exchanger 10 (FIG. 3, point 4). One part of therefrigerant is bypassed through the injection circuit 13. The other partof the refrigerant is cooled by the heat exchange with the refrigerantthat is to be sucked into the compressor 3 in the intermediate-pressurereceiver 9 (FIG. 3, point 5). The other part of the refrigerant isdecompressed to a low pressure in the third expansion valve 8, changinginto a two-phase refrigerant (FIG. 3, point 6). Then, the refrigerantflows from the outdoor unit 1 to the indoor unit 2 through the liquidpipe 7. Then, the two-phase refrigerant flows into the indoor heatexchanger 6, which serves as an evaporator. The refrigerant absorbs heatto evaporate (FIG. 3, point 7) while it supplies cold energy to the loadmedium, such as air or water, in the indoor unit 2. The low-pressure gasrefrigerant flowing out from the indoor heat exchanger 6 flows from theindoor unit 2 to the outdoor unit 1 through the gas pipe 5. The gasrefrigerant flows through the four-way valve 4, is heated by heatexchange with the high-pressure refrigerant in the intermediate-pressurereceiver 9 (FIG. 3, point 8), and is sucked into the compressor 3.

On the other hand, the refrigerant bypassed through the injectioncircuit 13 is decompressed to an intermediate pressure with the secondexpansion valve 14 and changes into a low-temperature two-phaserefrigerant (FIG. 3, point 9). Then, the low-temperature two-phaserefrigerant exchanges heat with the high-pressure refrigerant in thesecond internal heat exchanger 10, is heated in the heat source 17 (FIG.3, point 10), and is injected into the compressor 3. In the compressor3, the sucked refrigerant (FIG. 3, point B) is compressed to anintermediate pressure, is heated (FIG. 3, point 11), and is merged intothe injected refrigerant. The merged refrigerant having a reducedtemperature (FIG. 3, point 12) is again compressed to a high pressureand is discharged (FIG. 3, point 1). The heat source 17 for heating arefrigerant can adjust the amount of heat when necessary.

The PH diagram of the cooling operation is almost identical with that ofthe heating operation. Thus, similar operations can be achieved in bothoperation modes.

The control action of the refrigeration/air conditioning equipment willbe explained below. First, the control action in the heating operationwill be described with reference to FIG. 4. FIG. 4 is a flow chartshowing the control action in the heating operation. In the heatingoperation, the capacity of the compressor 3, the degree of opening ofthe first expansion valve 11, the degree of opening of the secondexpansion valve 14, and the degree of opening of the third expansionvalve 8 are set to initial values at step S1. At step S2, after theexpiration of a predetermined time, each actuator is controlled asfollows in a manner that depends on its operational status. The capacityof the compressor 3 is basically controlled such that the airtemperature measured with the tenth temperature sensor 16j in the indoorunit 2 is equal to a temperature set by a user of the refrigeration/airconditioning equipment.

In other words, the air temperature of the indoor unit 2 is comparedwith the set temperature at step S3. When the air temperature is thesame as or close to the set temperature, the capacity of the compressor3 is maintained to proceed to the step S5. When the air temperature isdifferent from the set temperature, the capacity of the compressor 3 isadjusted at step S4 in the following manner. When the air temperature ismuch lower than the set temperature, the capacity of the compressor 3 isincreased. When the air temperature is much higher than the settemperature, the capacity of the compressor 3 is decreased.

Each expansion valve is controlled in the following manner. The thirdexpansion valve 8 is controlled such that the degree of supercooling SCof the refrigerant at the outlet of the indoor heat exchanger 6, whichis obtained from the difference between the saturation temperature ofthe high-pressure refrigerant measured by the eighth temperature sensor16h and the outlet temperature of the indoor heat exchanger 6 measuredby the ninth temperature sensor 16i, is equal to a predetermined targetvalue, for example, 10° C. The degree of supercooling SC of therefrigerant at the outlet of the indoor heat exchanger 6 is comparedwith the target value at step S5. When the degree of supercooling SC ofthe refrigerant is greater than the target value at the step S5, thedegree of opening of the third expansion valve 8 is increased at step 6.When the degree of supercooling SC of the refrigerant is smaller thanthe target value at the step 5, the degree of opening of the thirdexpansion valve 8 is decreased at the step S6.

The first expansion valve 11 is controlled such that the degree ofsuperheat SH of the refrigerant sucked into the compressor 3, which isobtained from the difference between the suction temperature of thecompressor 3 measured by the sixth temperature sensor 16f and thesaturation temperature of the low-pressure refrigerant measured by thethird temperature sensor 16c, is equal to a predetermined target value,for example, 10° C. In other words, the degree of superheat SH of therefrigerant, which is the temperature of the refrigerant sucked into thecompressor 3, is compared with the target value at step S7. When thedegree of superheat SH of the refrigerant sucked into the compressor 3is equal or close to the target value, the degree of opening of thefirst expansion valve 11 is maintained to proceed to the next step S9.When the degree of superheat SH is different from the target value, thedegree of opening of the first expansion valve 11 is changed at step S8in the following manner. When the degree of superheat SH of therefrigerant sucked into the compressor 3 is greater than the targetvalue, the degree of opening of the first expansion valve 11 isincreased, and when the degree of superheat SH of the refrigerant issmaller than the target value, the degree of opening of the firstexpansion valve 11 is decreased.

Next, the second expansion valve 14 is controlled such that thedischarge temperature of the compressor 3 measured by the firsttemperature sensor 16a is equal to a predetermined target value, forexample, 90° C. In other words, the discharge temperature of thecompressor 3 is compared with the target value at step S19. When thedischarge temperature of the compressor 3 is equal or close to thetarget value at the step S9, the degree of opening of the secondexpansion valve 14 is maintained and the operation loops back to thestep 2.

When the degree of opening of the second expansion valve 14 is changed,the state of the refrigerant changes as follows. When the degree ofopening of the second expansion valve 14 increases, the flow rate of therefrigerant flowing into the injection circuit 13 increases. The amountof heat exchanged in the second internal heat exchanger 10 does notchange significantly with the flow rate of the refrigerant in theinjection circuit 13. Thus, when the flow rate of the refrigerantflowing through the injection circuit 13 increases, the enthalpydifference of the refrigerant (FIG. 2, difference between point 9 andpoint 10) in the injection circuit 13 at the second internal heatexchanger 10 decreases. Thus, the enthalpy of the refrigerant to beinjected (FIG. 2, point 10) decreases.

Accordingly, after the injected refrigerant is merged, the enthalpy ofthe refrigerant (FIG. 2, point 12) decreases. This also decreases theenthalpy and the temperature of the refrigerant discharged from thecompressor 3 (FIG. 2, point 1). Conversely, when the degree of openingof the second expansion valve 14 decreases, the enthalpy and thetemperature of the refrigerant discharged from the compressor 3increase. Thus, the degree of opening of the second expansion valve 14is controlled at step S10 such that when the discharge temperature ofthe compressor 3 is higher than a target value, the degree of opening ofthe second expansion valve 14 is increased, and when the dischargetemperature is lower than the target value, the degree of opening of thesecond expansion valve 14 is decreased. Then, the operation loops backto the step 2.

Next, the control action during the cooling operation will be describedwith reference to FIG. 5. FIG. 5 is a flow chart showing the controlaction in the cooling operation. In the cooling operation, the capacityof the compressor 3, the degree of opening of the first expansion valve11, the degree of opening of the second expansion valve 14, and thedegree of opening of the third expansion valve 8 are set to initialvalues at step S11. At step S12, after the expiration of a predeterminedtime, each actuator is controlled as follows in a manner that depends onits operational status.

First, the capacity of the compressor 3 is basically controlled suchthat the air temperature measured with the tenth temperature sensor 16jin the indoor unit 2 is equal to a temperature set by a user of therefrigeration/air conditioning equipment. In other words, the airtemperature of the indoor unit 2 is compared with the set temperature atstep S13. When the air temperature is the same as or close to the settemperature, the capacity of the compressor 3 is maintained to proceedto step S15. When the air temperature is different from the settemperature the capacity of the compressor 3 is adjusted at step S14 inthe following manner. When the air temperature is much higher than theset temperature, the capacity of the compressor 3 is increased. When theair temperature is lower than the set temperature, the capacity of thecompressor 3 is decreased.

Each expansion valve is controlled in the following manner. The firstexpansion valve 11 is controlled such that the degree of supercooling SCof the refrigerant at the outlet of the outdoor heat exchanger 12, whichis obtained from the difference between the saturation temperature ofthe high-pressure refrigerant measured by the temperature sensor 16c andthe outlet temperature of the outdoor heat exchanger 12 measured by thetemperature sensor 16d, is equal to a predetermined target value, forexample, 10° C. In other words, the degree of supercooling SC of therefrigerant at the outlet of the outdoor heat exchanger 12 is comparedwith the target value at step S15. When the degree of supercooling SC atthe outlet of the outdoor heat exchanger 12 is equal or close to thetarget value, the degree of opening of the first expansion valve 11 ismaintained to proceed to the next step S17. The degree of opening of thefirst expansion valve 11 is changed at step S16 such that when thedegree of supercooling SC at the outlet of the outdoor heat exchanger 12is greater than the target value, the degree of opening of the firstexpansion valve 11 is increased, and when the degree of supercooling SCof the refrigerant is smaller than the target value, the degree ofopening of the first expansion valve 11 is decreased.

Next, the third expansion valve 8 is controlled such that the degree ofsuperheat SH of the refrigerant sucked into the compressor 3, which isobtained from the difference between the suction temperature of thecompressor 3 measured by the sixth temperature sensor 16f and thesaturation temperature of the low-pressure refrigerant measured by theeight temperature sensor 16h, is equal to a predetermined target value,for example, 10° C. In other words, the degree of superheat SH of therefrigerant sucked into the compressor 3 is compared with the targetvalue at step S17. When the degree of superheat SH of the refrigerantsucked into the compressor 3 is equal or close to the target value, thedegree of opening of the third expansion valve 8 is maintained toproceed to the next step S19. When the degree of superheat SH isdifferent from the target value, the degree of opening of the thirdexpansion valve 8 is changed at step S18 such that when the degree ofsuperheat SH of the refrigerant sucked into the compressor 3 is greaterthan the target value, the degree of opening of the third expansionvalve 8 is increased, and when the degree of superheat SH of therefrigerant is smaller than the target value, the degree of opening ofthe third expansion valve B is decreased.

Next, the second expansion valve 14 is controlled such that thedischarge temperature of the compressor 3 measured by the firsttemperature sensor 16a is equal to a predetermined target value, forexample, 90° C. In other words, the discharge temperature of thecompressor 3 is compared with the target value at step S19. When thedischarge temperature of the compressor 3 is equal or close to thetarget value, the degree of opening of the second expansion valve 14 ismaintained and the operation loops back to the step 12. The variationsin the state of the refrigerant at the time when the degree of openingof the second expansion valve 14 is changed are similar to those in theheating operation. Thus, the degree of opening of the second expansionvalve 14 is controlled such that when the discharge temperature of thecompressor 3 is higher than the target value, the degree of opening ofthe second expansion valve 14 is increased, and when the dischargetemperature is lower than the target value, the degree of opening of thesecond expansion valve 14 is decreased. Then, the operation loops backto the step S12.

Next, the circuitry of the Embodiment 1 and operations and effectsachieved by the controls will be described. Since both the coolingoperation and the heating operation can be performed in a similar way inthis equipment, the heating operation is representatively describedbelow. The circuitry of the equipment is a so-called gas injectioncircuit. In other words, after the refrigerant flows out from the indoorheat exchanger 6, which serves as a condenser, and is decompressed to anintermediate pressure, a gas component of the refrigerant is injectedinto a compressor 3.

In typical refrigeration/air conditioning equipment, theintermediate-pressure refrigerant is often separated into liquid and gaswith a gas-liquid separator and is then injected. However, in therefrigeration/air conditioning equipment according to this embodiment,as shown in FIG. 6, the refrigerant is thermally separated into liquidand gas by heat exchange in the second internal heat exchanger 10, andis then injected.

The gas injection circuit has the following effects. The gas injectionincreases the flow rate of the refrigerant discharged from thecompressor 3: the flow rate of the refrigerant discharged from thecompressor 3 Gdis=the flow rate of the refrigerant sucked into thecompressor 3 Gsuc+the flow rate of the injected refrigerant Ginj. Thisincreases the flow rate of the refrigerant flowing into the heatexchanger, which serves as a condenser, and thereby increases theheating capacity in the heating operation.

On the other hand, as shown in FIG. 6, the heat exchange in the secondinternal heat exchanger 10 decreases the enthalpy of the refrigerantflowing into the heat exchanger, which serves as an evaporator. Thus,the difference in the enthalpy of the refrigerant in the evaporatorincreases. Accordingly, the cooling capacity also increases in thecooling operation.

Furthermore, the gas injection also improves the efficiency. Therefrigerant flowing into the heat exchanger, which serves as anevaporator, is generally a gas-liquid two-phase refrigerant, the gascomponent of which does not contribute to cooling capacity. However, thecompressor 3 does work of increasing the pressure of this low-pressuregas refrigerant, in addition to the gas refrigerant vaporized in theevaporator. In the gas injection, part of the gas refrigerant flowinginto the evaporator is drawn at an intermediate pressure, is injectedinto the compressor 3, and is compressed from the intermediate pressureto high pressure. Thus, there is no need to compress the gas refrigerantto be injected from low pressure to intermediate pressure. This improvesthe efficiency. This effect can be achieved in both the heatingoperation and the cooling operation.

Next, the correlation between the gas-injection flow rate and theheating capacity will be described. When the gas-injection flow rate isincreased, as described above, the flow rate of the refrigerantdischarged from the compressor 3 increases, but the dischargetemperature of the compressor 3 decreases, and the temperature of therefrigerant flowing into the indoor heat exchanger 6, which serves as acondenser, also decreases. In terms of the heat-exchange performance ofthe condenser, the amount of exchanged heat generally increases as thetemperature distribution in the heat exchanger extends. FIG. 7 shows thechanges in the refrigerant temperature at the time when the condensationtemperatures are the same but the refrigerant temperatures at the inletof the condenser are different. The temperature distributions at aportion where the refrigerant in the condenser is in a superheated gasstate are different.

In the condenser, although the amount of heat exchanged in therefrigerant in a two-phase state at the condensation temperaturedominates, the amount of heat exchanged at a portion where therefrigerant is in a superheated gas state accounts for about 20% to 30%of the total amount of exchanged heat and has a significant impact onthe amount of exchanged heat. If an injection flow rate is too high andthe refrigerant temperature at a portion where the refrigerant is in asuperheated gas state lowers drastically, heat-exchange performance inthe condenser will decrease, resulting in low heating capacity. FIG. 8shows the correlation between the gas-injection flow rate and theheating capacity. The heating capacity reaches the maximum at a certaingas-injection flow rate.

Next, operations and effects of heat exchange in theintermediate-pressure receiver 9 between the refrigerant 9a forexchanging heat and the through-pipe 18a in the suction pipe 18 of thecompressor 3 according to the Embodiment 1 will be described. In theheating operation, the gas-liquid two-phase refrigerant flows into theintermediate-pressure receiver 9 from the third expansion valve 8. Thegas-liquid two-phase refrigerant is cooled by the heat exchange betweenthe through-pipe 18a in the suction pipe 18 of the compressor 3 and therefrigerant 9a in the intermediate-pressure receiver 9, and flows out asa liquid refrigerant. In the cooling operation, the gas-liquid two-phaserefrigerant at the outlet of the second internal heat exchanger 10 flowsinto the intermediate-pressure receiver 9, is cooled, and flows out as aliquid refrigerant. Thus, the enthalpy of the refrigerant flowing intothe indoor heat exchanger 6, which serves as an evaporator, decreases.This increases the difference in the enthalpy of the refrigerant in theevaporator. Accordingly, the cooling capacity also increases in thecooling operation.

On the other hand, the refrigerant to be sucked into the compressor 3 isheated, and the suction temperature increases. This also increases thedischarge temperature of the compressor 3. In the compression stroke ofthe compressor 3, the compression of the refrigerant having a highertemperature generally requires a greater amount of work for the samepressure increase. Thus, the effect on the efficiency of the heatexchange in the intermediate-pressure receiver 9 between the refrigerant9a for exchanging heat and the through-pipe 18a in the suction pipe 18of the compressor 3 influences both the increase in the performance dueto the greater enthalpy difference in the evaporator and the increase inwork of compression. When the increase in the performance due to thegreater enthalpy difference in the evaporator has a greater influence,the operational efficiency of the equipment increases.

The heat exchange in the intermediate-pressure receiver between therefrigerant 9a and the through-pipe 18a in the suction pipe 18 is mainlyperformed by a gas refrigerant in the gas-liquid two-phase refrigerantcoming into contact with the through-pipe 18a in the suction pipe 18 andcondensing into liquid. Thus, when the liquid refrigerant left in theintermediate-pressure receiver 9 decreases, the contact area between thegas refrigerant and the through-pipe 18a in the suction pipe 18increases. This increases the amount of heat exchanged. Conversely, whenthe liquid refrigerant left in the intermediate-pressure receiver 9increases, the contact area between the gas refrigerant and thethrough-pipe 18a in the suction pipe 18 decreases. This decreases theamount of heat exchanged.

Thus, the intermediate-pressure receiver 9 has the following effects.First, since the refrigerant flowing out the intermediate-pressurereceiver 9 is liquid, the refrigerant flowing into the second expansionvalve 14 in the heating operation is always a liquid refrigerant. Thisstabilizes the flow rate of the second expansion valve 14 and ensuresstable control and stable operation.

Furthermore, the heat exchange in the intermediate-pressure receiver 9stabilizes the pressure of the intermediate-pressure receiver 9, theinlet pressure of the second expansion valve 14, and the flow rate ofthe refrigerant flowing into the injection circuit 13. For example, loadfluctuations and associated fluctuations in the high pressure side causefluctuations in the pressure of the intermediate-pressure receiver 9.The heat exchange in the intermediate-pressure receiver 9 reduces suchpressure fluctuations. When the load increases and the high pressureincreases, the pressure of the intermediate-pressure receiver 9 alsoincreases. This increases the pressure difference from the low pressure.This also increases the temperature difference in the heat exchange inthe intermediate-pressure receiver 9, thus increasing the amount ofexchanged heat. The increase in the amount of exchanged heat enhancesthe condensation of the gas component of the gas-liquid two-phaserefrigerant flowing into the intermediate-pressure receiver 9, thussuppressing the pressure increase. Thus, the pressure increase of theintermediate-pressure receiver 9 is prevented. Conversely, when the loaddecreases and the high pressure decreases, the pressure of theintermediate-pressure receiver 9 also decreases. This reduces thepressure difference from the low pressure. This also reduces thetemperature difference in the heat exchange in the intermediate-pressurereceiver 9, thus decreasing the amount of exchanged heat. The decreasein the amount of exchanged heat prevents the condensation of the gascomponent of the gas-liquid two-phase refrigerant flowing into theintermediate-pressure receiver 9, suppressing the pressure decrease.Thus, the pressure decrease of the intermediate-pressure receiver 9 isprevented.

In this way, the heat exchange in the intermediate-pressure receiver 9autonomously generates variations in the amount of exchanged heat,following the fluctuations in the operational status. This prevents thepressure fluctuations of the intermediate-pressure receiver 9.

Furthermore, the heat exchange in the intermediate-pressure receiver 9stabilizes the operation of the equipment. For example, when the stateof the low-pressure side changes and the degree of superheat of therefrigerant at the outlet of the outdoor heat exchanger 12 serving as anevaporator increases, the temperature difference in the heat exchange inthe intermediate-pressure receiver 9 decreases. Thus, the amount of heatexchanged decreases, and therefore the gas refrigerant is hardlycondensed. This increases the gas refrigerant level and decreases theliquid refrigerant level in the intermediate-pressure receiver 9. Thedecrement of the liquid refrigerant is carried over into the outdoorheat exchanger 12, increasing the liquid refrigerant level in theoutdoor heat exchanger 12. This suppresses the increase in the degree ofsuperheat of the refrigerant at the outlet of the outdoor heat exchanger12, thus suppressing the operational fluctuations of the equipment.Conversely, when the state of the low-pressure side changes and thedegree of superheat of the refrigerant at the outlet of the outdoor heatexchanger 12 serving as an evaporator decreases, the temperaturedifference in the heat exchange in the intermediate-pressure receiver 9increases. Thus, the amount of exchanged heat increases, and thereforethe gas refrigerant is easily condensed. This decreases the gasrefrigerant level and increases the liquid refrigerant level in theintermediate-pressure receiver 9. The increment of the liquidrefrigerant is derived from the outdoor heat exchanger 12, thusdecreasing the liquid refrigerant level in the outdoor heat exchanger12. This suppresses the decrease in the degree of superheat of therefrigerant at the outlet of the outdoor heat exchanger 12, thussuppressing the operational fluctuations of the equipment.

The suppression of the fluctuations in the degree of superheat alsoresults from autonomous generation of the variations in the amount ofexchanged heat, following the fluctuations in the operational status,through the heat exchange in the intermediate-pressure receiver 9.

Next, as in the Embodiment 1, the effect of the heat exchange in theintermediate-pressure receiver 9 in combination with the gas injectionfrom the injection circuit 13 will be described. The heat exchange inthe intermediate-pressure receiver 9 increases the suction temperatureof the compressor 3. Thus, in terms of the change in the compressor 3 inthe presence of the injection, the enthalpy of the refrigerantcompressed from a low pressure to an intermediate pressure (FIG. 2 andFIG. 3, point 11) increases, and the enthalpy of the refrigerant afterthe injected refrigerant is merged (FIG. 2 and FIG. 3, point 12) alsoincreases. Thus, the discharge enthalpy of the compressor 3 (FIG. 2 andFIG. 3, point 1) also increases, and the discharge temperature of thecompressor 3 increases. FIG. 9 shows the change in the correlationbetween the gas-injection flow rate and the heating capacity, dependingon the presence of the heat exchange in the intermediate-pressurereceiver 9. In the presence of the heat exchange in theintermediate-pressure receiver 9, the discharge temperature of thecompressor 3 is higher than that in the absence of the heat exchange atthe same injection level. This higher discharge temperature alsoincreases the temperature of the refrigerant at the inlet of thecondenser, the amount of heat exchanged in the condenser, and theheating capacity. Accordingly, the injection flow rate at the peak ofthe heating capacity increases. This also increases the peak value ofthe heating capacity, thus improving the heating capacity.

When further increase in the heating capacity is desired, a heat source17 for heating a refrigerant, such as an electric heater, is provided inthe injection circuit 13. The heat source 17 can suppress the decreasein the discharge temperature of the compressor 3 and increase theinjection flow rate. The heat source 17 can also increase the peak valueof the heating capacity, as shown in FIG. 9.

Furthermore, even in the absence of the heat exchange in theintermediate-pressure receiver 9, the degree of superheat at the inletof the compressor 3 and the discharge temperature of the compressor 3can be increased by controlling the degree of opening of the firstexpansion valve 11. However, in this case, the degree of superheat ofthe refrigerant at the outlet of the outdoor heat exchanger 12, whichserves as an evaporator, is also increased. This decreases the heatexchange efficiency of the outdoor heat exchanger 12. When the heatexchange efficiency of the outdoor heat exchanger 12 decreases, theevaporation temperature must be decreased to achieve the same amount ofexchanged heat. Thus, the low pressure is decreased in the operation.The decrease in the low pressure also decreases the flow rate of therefrigerant sucked into the compressor 3. Thus, such an operationcontrarily decreases the heating capacity. Conversely, in the presenceof the heat exchange in the intermediate-pressure receiver 9, therefrigerant at the outlet of the outdoor heat exchanger 12, which servesas an evaporator, is maintained in an appropriate state. Thus, thedischarge temperature of the compressor 3 can be increased withexcellent heat exchange efficiency. Thus, the decrease in the lowpressure as described above can be avoided, and the heating capacity canbe easily increased.

Furthermore, in the circuitry of the Embodiment 1, part of thehigh-pressure refrigerant is bypassed, is decompressed, is superheatedinto a gas in the second internal heat exchanger 10, and is injected.Thus, as compared with conventional equipment in which a gas separatedwith a gas-liquid separator is injected, the distribution of therefrigerant does not fluctuate when the injection level changes inresponse to the variations in control or operational status. Thus, morestable operation can be achieved.

In terms of the structure for performing the heat exchange in theintermediate-pressure receiver 9, any structure can achieve a similareffect, provided that the heat is exchanged with the refrigerant in theintermediate-pressure receiver 9. For example, the suction pipe of thecompressor 3 may be in contact with the outer periphery of theintermediate-pressure receiver 9 for heat exchange.

Furthermore, the refrigerant supplied to the injection circuit 13 may besupplied from the bottom of the intermediate-pressure receiver 9. Inthis case, in both the cooling operation and the heating operation, aliquid refrigerant flows into the second expansion valve 14. Thus, theflow rate at the second expansion valve 14 is consistent. This ensuresthe control stability.

As described above, the second expansion valve 14 is controlled suchthat the discharge temperature of the compressor 3 is equal to thetarget value. This target value is determined to provide the maximumheating capacity. As shown in FIG. 9, on the basis of the correlationamong the gas-injection flow rate, the heating capacity, and thedischarge temperature, there is a discharge temperature at which theheating capacity reaches the maximum. Thus, this discharge temperatureis previously determined and is employed as the target value. The targetvalue of the discharge temperature is not necessarily a constant value.The target value may be changed as required in a manner that depends onthe operating condition or characteristics of an apparatus, such as acondenser. In this way, the gas injection level can be adjusted toachieve the maximum heating capacity by controlling the dischargetemperature.

The gas injection level can be adjusted not only to achieve the maximumheating capacity, but also to achieve the maximum operationalefficiency. When a large heating capacity is required, for example,during the startup of the refrigeration/air conditioning equipment, thegas injection level is adjusted to achieve the maximum heating capacity.When the room temperature has increased after the equipment operates fora certain period of time and large heating capacity is no longerrequired, the gas injection level is adjusted to achieve the maximumefficiency. FIG. 10 shows the correlation among the injection flow rate,the heating capacity, and the operational efficiency. At the maximumoperational efficiency, the injection flow rate is smaller and thedischarge temperature is higher than those at the maximum heatingcapacity. At the injection flow rate at which the heating capacityreaches the maximum, since the discharge temperature is lower, theheat-exchange performance of the condenser decreases. In addition,because the intermediate pressure is decreased to increase the injectionflow rate, work of compressing the injected refrigerant increases. Thus,the efficiency is lower than that at the maximum operational efficiency.

Thus, as a target value of the discharge temperature controlled with thesecond expansion valve 14, not only a target value that provides themaximum heating capacity, but also a target value that provides themaximum operational efficiency are taken into consideration. Accordingto the operational conditions, for example, the operation capacity ofthe compressor 3 or the air temperature of the indoor unit side, whenthe heating capacity is required, the target value that provides themaximum heating capacity is specified, and when the heating capacity isnot required, the target value that provides the maximum operationalefficiency is specified. Such an operation can achieve both largeheating capacity and efficient operation.

As described above, the first expansion valve 11 is controlled to adjustthe degree of superheat at the inlet of the compressor 3 to the targetvalue. Such control can optimize the degree of superheat at the outletof the heat exchanger, which serves as an evaporator, ensuring excellentheat-exchange performance of the evaporator. In addition, such controlcan moderately ensure the difference in the enthalpy of the refrigerant,allowing the operation with high efficiency. While the degree ofsuperheat at the outlet of the evaporator that allows such an operationdepends on the characteristics of the heat exchanger, it is about 2° C.Since the refrigerant is further heated by the intermediate-pressurereceiver 9, the target value of the degree of superheat at the inlet ofthe compressor 3 is larger than this value. For example, the targetvalue is 10° C., as described above.

Thus, the first expansion valve 11 may be controlled such that thedegree of superheat at the outlet of the evaporator, or in the case ofthe heating operation the degree of superheat at the outlet of theoutdoor heat exchanger 12 obtained from the temperature differencebetween the second temperature sensor 16b and the third temperaturesensor 16c is equal to the target value, for example, 2° C. as describedabove. However, when the degree of superheat at the outlet of theevaporator is directly controlled and the target value is as low asabout 2° C., the refrigerant at the outlet of the evaporator istransiently in a gas-liquid two phase, which prevents appropriatedetermination of the degree of superheat. This makes the controldifficult. When the degree of superheat at the inlet of the compressor 3is detected, the target value can be increased. Furthermore, the heatingin the intermediate-pressure receiver 9 prevents the sucked refrigerantfrom being in gas-liquid two phase, and thereby prevents inappropriatedetection of the degree of superheat. This makes the control easier andstable.

As described above, the third expansion valve 8 is controlled to adjustthe degree of supercooling at the outlet of the indoor heat exchanger 6,which serves as a condenser, to the target value. Such control canensure excellent heat-exchange performance in the condenser andmoderately ensure the difference in the enthalpy of the refrigerant,allowing the operation with high efficiency. While the degree ofsupercooling at the outlet of the condenser that allows such anoperation depends on the characteristics of the heat exchanger, it isabout 5° C. to 10° C. Furthermore, the target value of the degree ofsupercooling may be higher than this value. For example, the targetvalue of about 10° C. to 15° C. allows the operation with increasedheating capacity. Thus, the target value of the degree of supercoolingmay be changed in a manner that depends on the operational conditions.During the startup of the equipment, the target value of the degree ofsupercooling may be slightly higher to ensure high heating capacity. Ata steady state at room temperature, the target value of the degree ofsupercooling may be slightly lower for the efficient operation.

The refrigerant of the refrigeration/air conditioning equipment is notlimited to R410A and may be another refrigerant.

Furthermore, the positions of the intermediate-pressure receiver 9 andthe second internal heat exchanger 10 are not limited to those in therefrigerant circuitry shown in FIG. 1. Even when the positionalrelationship between the upstream and the downstream is reversed, asimilar effect can be obtained. Furthermore, the position from which theinjection circuit 13 is drawn is not limited to that in the refrigerantcircuitry shown in FIG. 1. A similar effect can be obtained for anyposition, provided that the injection circuit 13 can be drawn fromanother intermediate-pressure portion and a high-pressure liquidportion. In view of the control stability of the second expansion valve14, the position from which the injection circuit 13 is drawn isdesirably the position at which the refrigerant is completely in aliquid phase rather than in a gas-liquid two phase.

In this Embodiment 1, the intermediate-pressure receiver 9, the secondinternal heat exchanger 10, and the injection circuit 13 are disposedbetween the first expansion valve 11 and the third expansion valve 8.Thus, in both the cooling operation and the heating operation, a similarinjection can be performed.

While the saturation temperatures of the refrigerant are measured withthe refrigerant temperature sensors in the middle of the condenser andthe evaporator, pressure sensors that can sense high pressure and lowpressure may be provided to determine the saturation temperatures fromthe measured pressures.

FIG. 11 is a flow chart showing the control action during the heatingand defrosting operation of the refrigeration/air conditioningequipment. In FIG. 11, the heating operation as described above isperformed, and at step S21 the capacity of the compressor 3, the degreeof opening of the first expansion valve 11, the degree of opening of thesecond expansion valve 14, and the degree of opening of the thirdexpansion valve 8 are set to initial values. At step S22, after theexpiration of a predetermined time, each actuator is controlled asfollows on the basis of its operational status. The capacity of thecompressor 3 is basically controlled such that an outdoor pipingtemperatures measured with the second temperature sensor 16b, the thirdtemperature sensor 16c, and the fourth temperature sensor 16d in theoutdoor unit 1 are equal to a temperature set by a user of therefrigeration/air conditioning equipment.

In other words, the outdoor piping temperature of the outdoor unit 1 iscompared with the set temperature at step S23. When the outdoor pipingtemperature is equal to or less than the set temperature (for example,−5° C.), it is concluded that frost forms on the outdoor heat exchanger12, which serves as an evaporator. Then, the four-way valve is rotatedto start a defrosting operation at step S24. To be more specific, thedefrosting operation is performed by passing a high-pressurehigh-temperature refrigerant discharged from the compressor 3 throughthe outdoor heat exchanger 12, as in the cooling cycle. While thedecrease in the discharge temperature is suppressed by opening thesecond expansion valve 14 and heating the refrigerant with the heatsource 17, the circulating volume of the refrigerant flowing into thecondenser is increased by the gas injection. This reduces the time ofthe defrosting operation.

Next, at step S25, the outdoor piping temperature is compared with theset temperature. When the outdoor piping temperature is equal to or morethan the set temperature (for example, 8° C.), it is concluded thatfrost has melted, and the operation proceeds to step S26. The four-wayvalve 4 is rotated to return to the heating operation and restart theoperation. While the decrease in the discharge temperature is suppressedby opening the second expansion valve 14, carrying out the injection,and heating the refrigerant with the heat source 17, as in thedefrosting operation, the circulating volume of the refrigerant flowinginto the condenser is increased. In addition, increased heating capacityaccelerates the startup of the heating operation. Next, at step S27, theindoor piping temperature is compared with a set temperature. When theindoor piping temperature is equal to or less than the set temperature,go to step S28. The second expansion valve 14 is closed to finish theinjection. Heating by the heat source 17 is also completed.

Next, operations and effects during the heating and defrosting operationwill be described. In the defrosting operation, frost forming onrefrigerant pipe of the outdoor heat exchanger 12 during the heatingoperation is melted by the heat of the refrigerant. This is performed byrotating the four-way valve 4 to flow the refrigerant as in the coolingoperation. At the same time, the second expansion valve 14 is opened toinject a gas into the compressor 3. This increases the flow rate of therefrigerant discharged from the compressor 3 and the flow rate of therefrigerant flowing into the outdoor heat exchanger 12, which serves asa condenser. On the other hand, as described above, the dischargetemperature of the compressor 3 tends to decrease. Thus, theheat-exchange performance of the condenser is also maximized in thiscase.

More specifically, as shown in FIG. 12, there is a gas-injection flowrate at which the defrosting time is minimized. Furthermore, in thisembodiment, the heat exchange in the intermediate-pressure receiver 9provides further improvement, that is, shortening of the defrostingtime.

Furthermore, when the heating operation is started after the completionof the defrosting operation, the gas injection can provide high heatingcapacity, that is, enhance the startup of the heating operation.

The use of the heat source for heating a refrigerant, such as anelectric heater, provided in the injection circuit 13, can suppress thedecrease in the discharge temperature of the compressor 3 and increasethe amount of refrigerant to be injected. This can further shorten thedefrosting time. In addition, another use of the heat source for heatinga refrigerant during a return to the heating operation can furtherenhance the startup of the heating operation.

While in the foregoing description the period of the injection during areturn to the heating operation is defined as a period until the heatingcapacity reaches a predetermined value, even when the period of theinjection is controlled using the condensation temperature, or ispredefined, a similar effect can be achieved.

1. Refrigeration/air conditioning equipment comprising: a compressor; afour-way valve; an indoor heat exchanger; a first decompressor; and anoutdoor heat exchanger, wherein these components are coupled circularly,and heat is supplied from the indoor heat exchanger, therefrigeration/air conditioning equipment further comprising: anintermediate-pressure receiver disposed between the indoor heatexchanger and the first decompressor; a first internal heat exchangerthat exchanges heat between a refrigerant in the intermediate-pressurereceiver and a refrigerant in a suction pipe of the compressor; and aninjection circuit in which part of a refrigerant between the indoor heatexchanger and the first decompressor is bypassed and is injected into acompression chamber in the compressor, the injection circuit comprising:a second decompressor; a second internal heat exchanger that exchangesheat between a refrigerant having a pressure reduced by the seconddecompressor and the refrigerant between the indoor heat exchanger andthe first decompressor; and a heat source for heating a refrigerant,disposed between the second internal heat exchanger and the compressor.2. The refrigeration/air conditioning equipment according to claim 1,wherein a third decompressor is provided between the indoor heatexchanger and the intermediate-pressure receiver.
 3. Therefrigeration/air conditioning equipment according to claim 1, furthercomprising a controller for controlling the degree of superheat of arefrigerant sucked into the compressor or the degree of superheat of arefrigerant at the outlet of the outdoor hear exchanger to apredetermined value by adjusting the first decompressor.
 4. Therefrigeration/air conditioning equipment according to claim 1, furthercomprising a controller for controlling the discharge temperature or thedegree of superheat of a refrigerant at the outlet of the compressor toa predetermined value by adjusting the second decompressor.
 5. Therefrigeration/air conditioning equipment according to claim 2, furthercomprising a controller for controlling the degree of supercooling of arefrigerant at the outlet of the indoor heat exchanger to apredetermined value by adjusting the third decompressor.
 6. Therefrigeration/air conditioning equipment according to claim 2, furthercomprising a controller for controlling the degree of superheat of arefrigerant sucked into the compressor or the degree of superheat of arefrigerant at the outlet of the outdoor hear exchanger to apredetermined value by adjusting the first decompressor.
 7. Therefrigeration/air conditioning equipment according to claim 2, furthercomprising a controller for controlling the discharge temperature or thedegree of superheat of a refrigerant at the outlet of the compressor toa predetermined value by adjusting the second decompressor.
 8. Acontroller of heating equipment including a primary refrigerant circuitcomprising: a first heat exchanger that makes a refrigerant absorb heatof air; a compressor that sucks the refrigerant from the first heatexchanger; a second heat exchanger that provides a load side medium withheat of the refrigerant discharged from the compressor; a firstexpansion valve that decompresses the refrigerant flowing from thesecond heat exchanger to the first heat exchanger, wherein the firstheat exchanger, the compressor, the second heat exchanger and the firstexpansion valve are connected so as to circulate the refrigerant; aninjection circuit that merges part of the refrigerant flowing from thesecond heat exchanger toward the first heat exchanger with therefrigerant that is sucked by the compressor via the first heatexchanger to be compressed to an intermediate pressure; a third heatexchanger that is installed in the primary refrigerant circuit and theinjection circuit and supplies heat of the refrigerant flowing from thesecond heat exchanger toward the first heat exchanger to the refrigerantflowing in the injection circuit; a second expansion valve that isinstalled in the injection circuit and decompresses the refrigerantflowing in the injection circuit; a first temperature sensor thatdetects a discharge temperature of the refrigerant discharged from thecompressor; and a controller that controls an opening degree of thesecond expansion valve so that the discharge temperature detected by thefirst temperature sensor, which is correlated with the refrigerant flowamount flowing in the injection circuit, coincides with a predeterminedtarget value in order to adjust heating ability of the second heatexchanger by a refrigerant flow amount flowing in the injection circuit.9. The controller of the heating equipment of claim 8, wherein thecontroller controls such that the opening degree of the second expansionvalve is increased so as to decrease an enthalpy of the refrigerantflowing in the injection circuit when the discharge temperature detectedby the first temperature sensor is higher than the target value and theopening degree of the second expansion valve is decreased so as toincrease the enthalpy of the refrigerant flowing in the injectioncircuit when the discharge temperature is lower than the target value.10. The controller of the heating equipment of claim 8, comprising; asecond temperature sensor for detecting a temperature of the refrigerantin the first heat exchanger, and a fourth temperature sensor fordetecting a temperature of the refrigerant flowing into the compressor,wherein the controller calculates a degree of superheat of therefrigerant at a suction side of the compressor based on the temperaturedetected by the second temperature sensor and the temperature detectedby the fourth temperature sensor, and controls the first expansion valvesuch that a predetermined target value of the degree of superheat of therefrigerant is calculated.
 11. The controller of the heating equipmentof claim 8, wherein the injection circuit branches from between thesecond heat exchanger and the first expansion valve.
 12. The controllerof the heating equipment of claim 8, wherein the refrigerant is a CO2refrigerant.
 13. The controller of the heating equipment of claim 8,wherein the refrigerant is a HC type refrigerant.
 14. The controller ofthe heating equipment of claim 8, wherein the load side medium thatexchanges heat with the refrigerant discharged from the compressor inthe heat exchanger on the load side is air.
 15. The controller of theheating equipment of claim 8, wherein the load side medium thatexchanges heat with the refrigerant discharged from the compressor inthe heat exchanger on the load side is water.